Local agencies and county governments are continually in need of drug abuse prevalence estimates for planning and resource allocation. Several mathematical models exist, such as, multiple recapture censuses and synthetic estimator methods. These models can be adapted for use with "state-of-the-art" microcomputing devices and software. Applied Sciences Research (ASR) proposes to identify and adapt methodologies from the mathematical sciences for estimating drug abuse prevalence; and, to develop software templates to be used on microcomputers for the estimating procedures. During Phase I, ASR will study the feasibility for estimating the number of individuals who inject illicit substances subcutaneously (especially, heroin, cocaine, and amphetamines) and other multiple drug use. These drugs will be studied due to their high prevalence and their harmful physiological, social, and personal consequences. Most important, these drugs are often used by injection, puttig the users at high risk for HIV infection and other blood-borne diseases. During Phase II, ASR proposes to develop detailed documentation and "cookbook" user manuals and microcomputer software as a marketable product. Applied Sciences Research proposes to use small manageable data sets in Phase I in order to test and validate the procedures before full development of the software and adaptation to larger data sets in Phase II, such as, Standard Metropolitan Statistical Areas (SMSAs), large-sized counties, states, or other regional areas of the country. The product will be made commerically available through the public domain (user groups) and software houses.